The mileage is about 85 thousand km, and the HR16DE1.6 full aluminum engine is equipped with a 4 speed automatic transmission in 2007. Users reflect: the trunk of the car can not be opened with the button switch, and it can only be opened through the keyhole of the trunk. Fault diagnosis: in view of the analysis of the fault phenomenon, there are usually the following reasons: the related fuse damage, the trunk lock button switch and the door lock motor fault, the car body computer malfunction and the related line fault. Check the indoor and outdoor fuse is good, the trunk door lock button switch can be broken and normal, the door lock motor power and grounding experiment can open normally. With the instrument entering BCM (body computer) diagnosis, no trouble code, when reading data flow, press the trunk switch in any case, the data shows off state. Whether it is the line problem or BCM fault, it is not sure now, but the fault is definitely in the two place, so consult the relevant circuit diagram, the car through the left front door lock in the lock in the lock sensor for the back button switch and BCM to provide the iron control line, only open the left front door, left front door lock actuator 4 and 5 foot connection The switch closes, the trunk button switch and the BCM signal. At this time, the trunk can be opened by the button switch of the trunk to prevent the trunk from being opened when the parking is waiting, so only after opening the left front door can the trunk be opened. This is a safe design. According to the circuit diagram, when the left front door is opened, the 2 foot brown line of the trunk lock opener switch has a grounding signal. After measuring the line, it shows that the left front lock motor is good, the BCM behind the toolbox is removed, and the BCM30 foot is found to be empty, and the next No. 31 foot is orange. Like the color identification of the circuit diagram, the specific location is shown in Figure 2. This is strange, is the original factory's circuit icon injection wrong, with doubts along the BCM wire harness back check, found in the right A column on the right side of the dashboard, there is a bridge plug, is the circuit diagram of the M13 plug, after pulling down to find the plug has been flooded, serious oxidation corrosion, after cleaning treatment, measure the rear case lock opener The 1 leg blue line of the switch interconnects with the 31 foot orange of BCM, and the trunk can be opened normally at this time, which indicates that the original plant's circuit icons are incorrectly injected. Maintenance summary: the fault of the car is due to the dampness corrosion of the bridge plug in the middle of the A column, which causes bad lines to affect the normal work of the electrical system of the trunk. Later several cases of the same failure, even with the smart key and the trunk remote control are also most of the reason, so on this type of car must pay attention to the electrical plug's waterproof work, and a small number of cars are caused by the left front door lock motor. Therefore, it is necessary to have a certain understanding of the control principle of the vehicle before the maintenance of the vehicle, so that we can quickly and accurately determine the fault point and avoid the curve. Maintenance review: the author of this article is correct in removing the fault of the car. As the rear case of the car can not be opened with the button switch, it can only be opened through the backroom spoon hole. This indicates that the fault point is not in the mechanical part. It should be the problem of the control line. One thing is worth affirming: the author carefully analyzes the control circuit of the vehicle when checking the fault. The inspection process only disconnects the BCM plug, then disconnects the trunk lock plug, and uses the multimeter ohm gear to check the connection between the terminal of the trunk and the BCM plug terminal. If the circuit breaker or the obstruction is too large, the connection of the plug between the lines should be considered firmly and whether the circuit is broken or not. The author carefully analyzed the control circuit of the vehicle when excluding the vehicle malfunction, so he eliminated the trouble in a short time.